export default (len = 32) => {
  return 'xxxxxxxxxxxx4xxxyxxxxxxxxxxxxxxx'.replace(/[xy]/g, function (c) {
    const r = (Math.random() * 16) | 0;
    const v = c === 'x' ? r : ((r & 0x3) | 0x8);

    return v.toString(16);
  }).substring(0, len);
}